Interfacial Reconstructed Layer Controls the Orientation of Monolayer Transition-Metal Dichalcogenides

Abstract

Growing continuous monolayer films of transition-metal dichalcogenides (TMDs) without the disruption of grain boundaries is essential to realize the full potential of these materials for future electronics and optoelectronics, but it remains a formidable challenge. It is generally believed that controlling the TMDs orientations on epitaxial substrates stems from matching the atomic registry, symmetry, and penetrable van der Waals forces. Interfacial reconstruction within the exceedingly narrow substrate-epilayer gap has been anticipated. However, its role in the growth mechanism has not been intensively investigated. Here, we report the experimental conformation of an interfacial reconstructed (IR) layer within the substrate-epilayer gap. Such an IR layer profoundly impacts the orientations of nucleating TMDs domains and, thus, affects the materials' properties. These findings provide deeper insights into the buried interface that could have profound implications for the development of TMD-based electronics and optoelectronics.

Epitaxy of wafer-scale single-crystal MoS2 monolayer via buffer layer control

“…This suggests that the buffer layer within the substrate-epilayer gap is the key to facilitate the unidirectional epitaxy of the monolayer MoS 2 and has been recently demonstrated for unidirectional MoS 2 epitaxy on β -Ga 2 O 3 (Fig. 1h ) 35 . It is noteworthy that for previously reported unidirectional TMDs on sapphire substrates, a buffer layer is also typically observed, but its role is usually ignored 19 , 20 , 34 .…”

Tuning the Electronic and Photoelectronic Properties of Two-Dimensional MoSe2 Thin Films by In Situ V-Doping

“…2D TMDs, such as MoS 2 , − MoSe 2 , WS 2 , WSe 2 , and MoTe 2 , are the most typical class of 2D materials with semiconductor properties. − 2D TMDs have excellent electrical, optical, and spin-related properties, which make them widely used in nanoscale optoelectronics and spintronics, opening up a new path for the development of 2D materials. − As a typical representative of 2D TMDs, 2D MoSe 2 has potential applications in the semiconductor field. For example, single-layer MoSe 2 is a direct-band-gap semiconductor material and its photoelectric conversion efficiency is higher than that of few-layer MoSe 2 , making it widely used in the fields of photoelectric devices, such as transistors, , diodes, , photodetectors, and photovoltaic cells .…”

Efficient Carrier Multiplication in Self-Powered Near-Ultraviolet γ-InSe/Graphene Heterostructure Photodetector with External Quantum Efficiency Exceeding 161%

“…Two-dimensional (2D) layered materials, such as graphene (Gr), black phosphorus, transition metal dichalcogenides, and hexagonal boron nitride, are free of dangling bonds and exhibit excellent electronic and optoelectronic properties. − More importantly, the performance (threshold and efficiency) of carrier multiplication (CM), which yields two or more electron–hole pairs by absorbing one high-energy photon, is superior in 2D materials compared to conventional bulk semiconductors, owing to enhanced Coulomb interaction and relaxed momentum conservation. , Furthermore, 2D materials maintain a high density of states in the plane, combined with high carrier mobility, which gives them a significant advantage over colloidal quantum confined nanocrystals for carrier extraction and transport in CM processes. Taking Gr for example, , high-energy photons in the UV region can induce more steps of impact excitation cascade, resulting in a more significant CM effect and higher efficiency.…”